This invention relates to optically activated radiation intensity control devices and more particularly to such control devices which have a quick response to illuminating radiation and a rapid recovery subsequent to extinction which provides protection against intense fast rising pulses of optical radiation.
Optically activated radiation shutter attenuators have been provided heretofore for protection of the eyes, etc. These devices fall into two categories-passive and active. Passive devices are characterized as those such as sunglasses or other eye protectors which darken due to cross-linking of polymer chains due to exposure to ultraviolet radiation. Such known devices have a relatively long activation and recovery time. Active devices include those electro-optic devices which can be made attenuating with the application of a voltage between electrodes. Such systems require a radiation detector which controls a voltage applied to the electrodes. Voltage on the electrodes then controls the radiation passage characteristics of the optical devices. Such systems usually require high voltages, and often require bulky equipment; however, they can have a time responses of several nsec. Various types of prior art devices are set forth in U.S. Pat. Nos. 3,269,267; 3,370,902; 3,436,144; 3,507,552; and 3,756,692.